Mercedes-Benz GLS-Class, X166 (USA / CAN)

Coolant capacity & service interval

Mercedes-Benz GLS-Class, X166 (USA / CAN) uses coolant with a capacity range of 7,5 to 12,9 liters. The service interval is 150000 miles or 180 months. The data covers 6 configurations.

The configuration chart below lists fill volumes and service intervals for each engine and trim variant.

TypeSpecifications
GLS 350 d 4MATIC, 166.823/824 (2017-2019)
  • Use: Normal
  • Between min and max.
  • Change 150000 miles/ 180 months
GLS 450 4MATIC, 166.864 (2017-2019)
  • Use: Normal
  • Capacity 10,5 liter
  • Change 150000 miles/ 180 months
GLS 350 d 4MATIC, 166.823/824 (2015-2017)
  • Use: Normal
  • Between min and max.
  • Change 150000 miles/ 180 months
GLS 450 4MATIC, 166.864 (2015-2017)
  • Use: Normal
  • Capacity 10,5 liter
  • Change 150000 miles/ 180 months
GLS 550 4MATIC, 166.873 (2015-2017)
  • Use: Normal
  • Capacity 12,9 liter
  • Change 150000 miles/ 180 months
GLS 63 AMG 4MATIC, 166.875 (2015-2019)
  • Use: Normal
  • Capacity 7,5 liter
  • Change 150000 miles/ 180 months

Additional Notes

  • The GLS 450 4MATIC (166.864) carries a cooling system capacity of 10.5 liters, a figure that reflects a full system fill including the engine block, radiator, and expansion reservoir.
  • The GLS 550 4MATIC (166.873) has the largest cooling system capacity among the petrol variants at 12.9 liters, consistent with the greater thermal load generated by a larger displacement V8 engine.
  • The GLS 63 AMG 4MATIC (166.875) specifies a cooling system capacity of 7.5 liters under normal use conditions, a notably lower figure than the GLS 550 despite housing a high-output AMG V8, which may reflect a more compact or differently routed cooling circuit design.
  • The GLS 350 d 4MATIC (166.823/824) does not list a fixed liter capacity, instead specifying that the coolant level should fall between the minimum and maximum marks on the reservoir. This approach is typical when precise total system volume is less relevant than maintaining the correct operating level during top-ups.
  • All configurations across the 2015-2019 model range share an identical service interval of 150,000 miles or 180 months under normal use conditions. The 180-month figure equals 15 years, placing this among the longest coolant change intervals in the industry and reflecting the long-term stability of modern silicate-free or organic acid technology (OAT) coolant formulations.
  • The GLS 350 d 4MATIC appears across two overlapping year ranges, 2015-2017 and 2017-2019, with identical specifications in both. The 2017 overlap corresponds to a mid-cycle production period where the chassis code 166.823/824 continued without a change to cooling system service requirements.
  • The same overlap pattern applies to the GLS 450 4MATIC (166.864), where the 2015-2017 and 2017-2019 entries carry the same 10.5-liter capacity and 150,000-mile interval, indicating no revision to cooling system specifications across that production span.

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